Tektronix 071-0130-00, User Manual, Page: 278 / 376

Using Features for Advanced Applications
TDS 500D, TDS 600B, & TDS 700D User Manual
3–217
Waveform Record — the complete waveform record acquired from an input
channel and displayed from the same channel or a reference memory. The length
of this time domain record is user-specified from the Horizontal menu. The
waveform record is not a DSP Math waveform.
FFT Time Domain Record — that part of the waveform record input to the FFT.
This time domain record waveform becomes the FFT math waveform after it’s
transformed. Its record length depends on the length of the waveform record defined
above.
FFT Frequency Domain Record — the FFT math waveform after digital signal
processing converts data from the FFT time domain record into a frequency
domain record.
Figure 3–100 compares the waveform record to the FFT time domain record.
Note the following relationships:
For waveform records
≤
10 K points in length, the FFT uses all of the
waveform record as input.
For waveform records
>
10 K points, the first 10 K points of the waveform
record becomes the FFT time domain record.
Each FFT time domain record starts at the beginning of the acquired
waveform record.
The zero phase reference point for a phase FFT math waveform is in the middle
of the FFT time domain record regardless of the waveform record length.
Zero Phase
Reference
Waveform Record
>
10 K
Waveform Record
≤
10 K
FFT Time Domain Record = 10k
FFT Time Domain Record =
Waveform Record
Zero Phase
Reference
Figure 3–100: Waveform Record vs. FFT Time Domain Record